Brugia malayi is a parasitic nematode that causes disseminated disease in the lymphatic and respiratory systems, in addition to chronic disfiguring elephantiasis. Accounts from ancient civilizations describe the role that filarial parasites have had on human hosts for centuries. Presently, the World Health Organization estimates over 140 million cases with over a billion people at risk for infection. All filarial parasites share a biphasic lifecycle within arthropod vectors and mammalian hosts, but only B. malayi can be cultured in the laboratory by passage through mosquitoes and gerbils, serving as a model for filariasis. B. malayi has six chromosomes (five autosomes and an XY sex-determining pair) comprising the estimated 110 Mb genome. The chromosomes are difficult to resolve individually and they are at the smallest 10 Mb in size. We propose to begin large-scale sequencing of the B. malayi NIAID/TRS strain genome by generating, in phase 1 of the project, 8 Mb of discontinuous single-pass sequence implemented by end-sequencing 8,000 BACs (Bacterial Artificial Chromosomes) from a large insert (greater than 100 kb) library to be constructed and from an already existing library (approximately 60 kb). The purpose of the first phase is to enhance early gene discovery and to provide markers that will be important for construction of a high-resolution sequence-ready map. During phase 2 of this proposal, 13 Mb of contiguous sequence will be generated representing chromosomal regions rich in genes that are of interest to the filarial community. These regions have been agreed upon by a consortium of filarial parasite experts around the world as being of most immediate biomedical importance as targets for new therapeutics or potential vaccine candidates. Chosen were also regions representing areas of evolutionary importance for which comparisons to genomes that have already been fully sequenced (such as the free-living nematode Caenorhabditis elegans) or to ESTs from a large collection of filariae will be the most informative. The genome sequence of B. malayi will provide invaluable information to researchers around the world, including the (1) identification of genes involved in basic functions of filarial parasites; (2) construction and mapping of BAC clones, which will facilitate easy, inexpensive and fast cloning of genes encoding proteins being actively studied by filariasis laboratories; (3) immediate access to genes and their products for functional/structural studies; (4) prediction of metabolic pathways on the basis of candidate genes; (5) identification of parasite-specific gene products by comparison with other genomes; and (6) starting point for whole-genome analysis of B. malayi.